1. Field of the Invention
The present invention relates to an insert type chain hoist, and in particular to a chain hoist installed in a rolling door driving device and provided for users to open or close a rolling door manually.
2. Description of the Related Art
Doors play an important role for ensuring the security of a premisis and to provide protection against the environment. However, a conventional rolling door employs a motor connected to a rotating shaft, such that the motor can drive the rotating shaft to rotate and drive the door panel to be rolled and unrolled to achieve the effects of opening and closing the rolling door. To prevent the rolling door from being unable to open or close during a power failure, a winch is installed at the back of the motor through a motor axle, so that users can use a hinge chain of the winch to pull the motor axle in order to roll or unroll the door panel.
However, such an arrangement has the following shortcomings:
1. Since the motor brakes on power failure or disconnection, users require a large force to pull the winch. If a gearbox is used to reduce the required pulling force, then the ascending or descending speed of the door panel will be significantly reduced (at present, most rolling doors adopt this method), and it usually takes more than ten minutes to open or close a rolling door.
2. A gearbox is used to reduce the required pulling force, and the volume of the gearbox is very large, and thus a large installation space is needed, and such arrangement is obviously not suitable for many situations.